FFmpeg recipe

FFmpeg: Change a Video's Frame Rate

fps=30 simply drops or duplicates frames to hit the target rate. For smoother motion (slow-mo, time-warp), use minterpolate instead.

Command

ffmpeg -i input.mp4 -vf fps=30 -c:v libx264 -crf 23 -c:a copy -y output_30fps.mp4

Prefer no terminal?

Use the FPS Converter in your browser

-i	Input file. Can be a video, audio, or image. Repeat for multiple inputs.
-vf	Video filter chain. e.g. scale=1280:720, crop=, fps=30.
-c:v	Video codec for output. e.g. libx264, libx265, libvpx-vp9.
-crf	Constant Rate Factor — quality target (lower = better, larger file). 23 is visually lossless for libx264.
-c:a	Audio codec for output. e.g. aac, libmp3lame, copy.
fps=30	Target frame rate. fps filter does naive drop / duplicate — safe but not motion-interpolated.

For smooth motion interpolation, use -vf "minterpolate=fps=60:mi_mode=mci". Slow but pretty.
For inverse telecine (24p in 60i), see -vf pullup,fps=24000/1001.

ffprobe -v error -show_entries stream=r_frame_rate -of csv=p=0 output.mp4

The target rate as a fraction, for example 30/1.

Going down duplicates nothing, going up does	fps=30 from 60 drops frames cleanly. fps=60 from 30 repeats them, which looks identical and doubles the size.
minterpolate for real smoothing	It invents intermediate frames rather than repeating them. It is slow and produces artefacts around fast edges.
Audio is untouched	Changing frame rate this way does not alter duration or pitch. That is setpts, and a different recipe.

Motion looks stuttery after converting to a higher rate.

Why: Frames were duplicated rather than generated, so there is no new motion information.

Fix: Use the minterpolate filter to synthesise intermediate frames, which is far slower but genuinely smoother.

Audio no longer lines up with the picture.

Why: The frame rate was changed by altering the timebase, which stretched the video against a fixed audio track.

Fix: Use the fps filter, which resamples frames while leaving duration alone, rather than setting -r on its own.